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94. Propulsion – Discussion

24/01/2014

There’s been a lot of heart-searching and discussion about propeller shapes since Theo went to pick up an example to copy from the Shuttleworth Collection.

The Shuttleworth propeller

The Shuttleworth propeller

Original Bristol propeller profileOriginal Bristol propeller profile

You can see from the photographs that the shape is significantly different from the one in the Bristol Scout parts list, and despite our best efforts – there is another Bristol Scout propeller at the Tangmere museum, and Leo Opdyke has one in New York state – none of them is the Bristol-made one intended for a le Rhône-engined Scout.

Rupert Wasey at Hercules propellers has looked at the markings on the Shuttleworth one, and says it was made by the Graham White company in Hendon, and they also clearly indicate it’s intended for an 80hp le Rhône, so we are confident it will work satisfactorily. It’s just that the shape of the Bristol propeller is quite distinctive, and we’ve got a nice original Bristol logo to go on it, and we wouldn’t be able to use it on a Graham White propeller!

Rupert also sent me an email suggesting a profile of a very different sort, that had its own attractions…

Rupert Wasey's suggestion for a very attractive profile

Rupert Wasey’s suggestion for a very attractive profile

Historically, of course, we’ve no idea which propeller Granddad used, since 1264 was something of a bodge job, with the engine from a Nieuport 11, and his having wrecked whichever propeller was originally fitted on its first flight post-modification! You could argue that the propeller might have come off the Nieuport as well, but they used one of considerably smaller diameter and pitch, and we don’t know whether that might over-speed the engine. Or he might have used a Bristol propeller – there were other le Rhône engined ones out there by that time. Or, since they had such a motley collection of aircraft out there, it might have been pretty much anything. In fact, there’s a photograph in the relevant Windsock publication of a Scout in France that was also converted to a le Rhône engine from a Nieuport, with a propeller looking much like the Shuttleworth one.

In the end, we’ve been persuaded by Rupert to go with the devil we know, rather than experiment with trying to modify it to look like the Bristol pattern. We don’t know that it’s inaccurate historically, and it is important, after all, that it does fly when we’re done!

The final word in this long saga is that poor Theo set off from Dorset to go to Hercules Propellers at Stroud, discussed all of this with Rupert before setting off to take the original back to the Shuttleworth Collection at Biggleswade and driving home again – a total of 370 miles, or seven and a half hours’ driving. Unfortunately, a few miles from home there was a bad accident on the A31, and he was stranded on the main rod, unable to move, for a further six hours, getting home at midnight.

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